[Tutor] learning curve

[Kent Johnson]

Daniel Klose wrote:
> Thanks Kent,
> 
> I now have:
> 
> target = sys.argv[1]
> 
> seqDictionary =  {} # python 2.5 import defaultdict from collections.
> structureArray = [0, 0, 0]
> 
> #THIS TAKES THE PLACE OF THE STANDARD PERL $DIR,$file
> #shorter to do the os.path.join once to a variable.
> if (os.path.isfile(os.path.join(structDir, target)) and
> os.path.isfile(os.path.join(seqDir, target))):
>     structureHandle = open(os.path.join(structDir, target))
>     structureString = structureHandle.readline()
>    
>     sequenceHandle  = open(os.path.join(seqDir, target))
>     sequenceString = sequenceHandle.readline()
> 
>     if len(structureString) == len(sequenceString):
>        
>         for strChar, seqChar in zip(structureString, sequenceString):
>             #SET DEFAULT VALUE AS ZERO ELSE INCREMENT
>             seqDictionary[seqChar] = seqDictionary.get(seqChar, 0) + 1
>             if (strChar.count('-')):

Since strChar is a single character you can just do
   if strChar == '-':
etc.

>                 structureArray[0] += 1
>             elif (strChar.count('H')):
>                 structureArray[1] += 1
>             elif (strChar.count('E')):
>                 structureArray[2] += 1
>             else:

You could put all of the above into a dict lookup, something like

offsets = { '-': 0, 'H': 1, 'E': 2 }	# this can be defined outside the loop
offset = offsets.get(strChr)
if offset is None:
   print strChar, " is not valid"
else:
   structureArray[offset] += 1

Or you could just use another dict for structureArray and index it by 
strChar directly.

>                 print strChar, " is not valid"
>                 break;
> else:
>     print "Some data is missing!\n"
> 
> The reason I want to create a dictionary of lists is because for each of
> the keys in the dictionary I wanted to keep tabs on the associated
> structure.  For example:
> 
> dictionary[A] = [0,0,0]
> 
> list x element = A
> list y element = '-'
> 
> then dictionary[A][0] = 1
> 
> print dictionary[A]
> : [1, 0, 0]
> 
> I thought that a dictionary would be the best way (it is the same way as
> I have done it in perl and java).  I am using google but having limited
> success.

You can easily make a dict whose values are lists or dicts. I'm not sure 
how the above pseudo-code fits in to your code but maybe you want 
something like this:

structureArray = structureDict.get(seqChar, [0, 0, 0])
# figure out offset as above
structureArray[offset] = 1 # or += 1 if you are keeping counts.

> *Do you folks bottom post or top post?  The users of the perl list are
> sensitive about this stuff!

We're pretty casual here on python-tutors but on comp.lang.python you 
will get scolded for top-posting and bottom-posting is more common here 
as well.
> 
> I am only running python 2.4 and the system admin doesn't like me so I
> won't ask him to upgrade it.